Northwest Corridor Project
The Northwest Corridor Project (formerly Northwest Corridor HOV/BRT) is a Georgia Department of Transportation (GDOT) plan currently under construction to put HOV and toll lanes (and originally bus rapid transit) along Interstate 75 and Interstate 575 in the northwestern suburbs of metro Atlanta. It will carry commuters between Atlanta and Cobb County, and beyond in Cherokee County, Georgia by adding two lanes for high-occupancy vehicles along I-75, with one continuing up a dedicated HOV exit onto I-575 to Sixes Road (mile 11, former exit 6), and the other straight on I-75 to Hickory Grove Road, just past Wade Green Road (mile 273, former exit 118). North of the highway interchange where they split, the new lanes would be put in the road median, between the existing northbound and southbound traffic. From the Perimeter (Interstate 285 on the northside) to I-575, the road has already been built with 12 to 16 lanes, which will require other plans, including via eminent domain.
Original plans
HOV-only exits would be built at roads which currently cross the highways, but have no access to it. Bus stations would also be built at these points, with park-and-ride parking lots. New lanes would be divided from the regular ones by concrete barriers, not just by white double-stripes as was done by GDOT inside the Perimeter. There were originally no plans to allow or even design for later contraflow lane usage for rush hours.
Truck lanes
There were also plans to add two truck-only lanes in each direction, further expanding the highway by another six lanes (including emergency lanes). However, the powerful trucking industry fought the idea of being required to use the tolled lanes. Separating traffic was proposed because it would smooth traffic and make the main lanes safer for cars. However, it would also effectively end the subsidy the industry gets by using roads which are mainly paid-for by the public (in contrast with railroads, which maintain their own tracks and pay per-mile taxes on them on top of that).
Criticisms
Criticisms of the plan include adding yet more lanes to already-oversized highways, and adding traffic to smaller roads by putting exits on them. Another major criticism is that it fails to consider commuter rail, light rail, or any other rail system seriously as an alternative. There are already state-owned rail tracks running CSX freight trains parallel to I-75, and Georgia Northeastern Railroad tracks branching off parallel to I-575, which would cost far less in terms of both money and disruption from construction. Though cleaner-burning natural gas buses would likely be used, there are no plans that call for them to be trolleybuses with an overhead double-catenary system, such as in Seattle and Vancouver. Part of the problem is also that Georgia's constitution prohibits state gasoline tax money from being spent on anything except roads, which makes other alternatives like trains very difficult to fund, even though their entire intent is to relieve roads. This was further worsened when the state sales tax was removed on gasoline and the gas tax was raised instead.
Cobb county is also considering a BRT system, but along Cobb Parkway instead, which a study showed would worsen traffic there. The state has abandoned BRT as a part of the Northwest Corridor project, although the city of Marietta has still purchased and demolished some of the affordable apartments that were to be eliminated for one of the BRT stations.
Scaled plans
Citing the enormous cost of the plan (around four billion dollars), in summer 2009 it was scaled back to putting two barrier-separated reversible lanes on I-75 to I-575, and one in the median on each road north of there. There would no longer be HOV exits on I-575, just slip roads to northbound and from southbound lanes for access to and from regular exits. It was not stated how much land would be taken on the southern portion. There was already a provision for a future HOV exit in the median at the Terrell Mill Road underpass, however the remainder has no median, only a wide left shoulder and a concrete barrier. It was also left unknown how the lanes would tie into the interchange at I-285.
Current progress
As of June 2016, all of the forest along the west-side right of way (and some additional land) of I-75 from I-285 to I-575 has been razed for the project, and some sections are nearly complete. A long viaduct over the Canton Highway Connector interchange and nearly over a factory was one of the first parts to be finished, followed by the crossover from the west side of the I-75 at I-575 to the east side of the median (west side of the northbound lanes) at Barrett Parkway. Curved bridges connecting to the median of I-285 east and west/south are under construction, and the connection to the I-575 median has recently begun, but the connection to and from I-75 south of I-285 has not yet been started.
The viaduct over Delk Road and its ramps is mostly complete except for the south end, but far less has been done at the adjacent Windy Hill Road and South Marietta Parkway interchanges, the latter of which will have the new lanes go over the ramps but under the road. Excavation and an initial concrete spraying for a retaining wall has been done there and under Allgood Road. At North Marietta Parkway (the only exit that is below the freeway or on an inside curve), the existing on and off ramps for southbound traffic have been moved closer to the freeway, and retaining walls that will carry the new lanes around the interchange have been built in their place, with no bridge yet underway. This is nearly up against a replacement water slide just installed at the Six Flags White Water waterpark on the southeast side. Grading has begun south of where Bell's Ferry Road passes underneath, and for the new HOV exit at Roswell Road (former Georgia 120, now Georgia 3 Connector). The formerly landscaped median at Terrell Mill has been built over and bridged in order to shift the existing southbound lanes, to make room for the new HOV exit there.
Construction is also underway north of the split past Chastain Road on I-75, including the final exit at Hickory Grove Road; and on I-575 up to around Georgia 92, plus the completed bridge structure over Towne Lake Parkway, and preliminary work for the Little River bridge.
The cost to state taxpayers is from 800 to 900 million dollars, far more than the HOT lanes on other local freeways due to the need for bridges, since the median had already been paved over on most of the route. It is set to be fully complete in 2017. A separate GDOT reconstruction of the interchange at Windy Hill Road is also underway and set to be complete in 2017. An independent widening of that road is occurring at the same time, largely to serve the new stadium, both funded by Cobb county taxpayers.